Volatile organic compounds (VOC's) in toner are released during fusing and can be detrimental to the environment and to the health of those working in close proximity to a printer. VOC's react with nitrogen oxides in the presence of sunlight to form ozone, a known irritant of the upper respiratory tract. In addition, VOC levels in toner have been linked to machine odor.
Ecolabel certifications, such as, Blue Angel (Germany) and Nordic Swan (Nordic Region), place limits on total volatile organic compounds (TVOC) in toner or limit total VOC emissions from a machine in use. One certification imposes a toner TVOC limit of less than 300 mg/kg.
Odor and VOC emission historically were addressed through reduction of VOC's in the toner or via air filtration systems at point of use. VOC's in a toner arise from the raw materials used to make toner, for example, as impurities in the monomer streams for making latex. Therefore, previous approaches focused on lower VOC raw materials.
However, many raw materials for latex production are commodity materials making identifying low VOC content materials difficult, if not impossible. In addition, suppliers of commodity materials may provide material with higher VOC level when supply assurance issues arise.
Treatment of latex monomer streams is difficult and expensive because the impurities often are chemically similar to the desired component (e.g., isopropyl benzene, the impurity, and styrene, the monomer). Also, the high solid content and chemical properties of latex make removal of VOC's after latex production difficult.
A large portion of toner is for aftermarket sale. There is no control over use of air filtration either as part of a machine or by end users. That makes VOC reduction in toner the only alternative for lowering VOC emissions.